Field of the Invention
The present invention relates to wireless communication and, more particularly, to a method for operating a user equipment (UE) in a wireless communication system and a device using the same.
Related Art
International Telecommunication Union Radio (ITU-R) communication sector is proceeding with standardization of an International mobile telecommunication (IMT)-Advanced, a next-generation mobile communication system following the 3rd-generation. The IMT-Advanced aims at supporting Internet protocol (IP)-based multimedia services at a data rate of 1 Gbps in a stationary and low-speed movement state and at a data rate of 100 Mbps in a high speed movement state.
3rd-generation partnership project (3GPP), a system standard that meets the requirements of the IMT-Advanced, provides long term evolution (LTE)-Advanced by improving the LTE which is based on an orthogonal frequency division multiple access (OFDMA)/single carrier-frequency division multiple access (SC-FDMA) transmission scheme. The LTE-advanced is one of potential candidates for the IMT-Advanced.
In the existing LTE-A, a maximum of five carriers (cells) are aggregated to provide carrier aggregation (CA), but, in a future wireless communication system, enhanced CA (eCA) of aggregating a maximum of 32 carriers (cells) is considered.
The increase in the number of aggregated carriers (cells) may cause various problems. For example, it may be difficult or impossible to effectively monitor downlink control information by an existing search space (SS) configuring method for searching for a control channel and the number of times of blind decoding (BS) of each aggregation level (AL).
Also, according to the existing scheme, only a maximum of eight carriers may be indicated unless a size of an existing 3-bit carrier indication field (CIF) included in downlink control information is changed for backward compatibility with a legacy terminal. Thus, it is indefinite how 32 carriers (cells) are to be indicated.
In addition, a maximum number of times of blind decoding that can be supported by each UE to detect downlink control information may differ depending on capabilities of UEs. Also, an amount of control information to be transmitted to each UE may differ depending on a channel state, a data amount currently required by each UE, and the like. These variables may further be increased as the number of carriers to be aggregated is increased.